Convert MS OS descriptor builder to a writer API

This brings it inline with the other embassy-usb descriptor APIs and allows it to integrate well with the Builder to allow class constructors to add MS OS descriptors.

Also adds a `usb_serial_winusb` example to demonstrate how to use the API.

1 files changed, 2 insertions, 1 deletions

diff --git a/embassy-usb/Cargo.toml b/embassy-usb/Cargo.toml
index 31d1f4cae..54a8f27c7 100644
--- a/embassy-usb/Cargo.toml
+++ b/embassy-usb/Cargo.toml
@@ -13,6 +13,7 @@ target = "thumbv7em-none-eabi"
 [features]
 defmt = ["dep:defmt", "embassy-usb-driver/defmt"]
 usbd-hid = ["dep:usbd-hid", "dep:ssmarshal"]
+msos-descriptor = ["dep:widestring"]
 default = ["usbd-hid"]
 
 [dependencies]
@@ -24,7 +25,7 @@ embassy-net-driver-channel = { version = "0.1.0", path = "../embassy-net-driver-
 defmt = { version = "0.3", optional = true }
 log = { version = "0.4.14", optional = true }
 heapless = "0.7.10"
-widestring = { version = "1.0.2", default-features = false }
+widestring = { version = "1.0.2", default-features = false, optional = true }
 
 # for HID
 usbd-hid = { version = "0.6.0", optional = true }